Charge balanced charge pump control

ABSTRACT

Operating a charge pump in which switches from a first set of switches couple capacitor terminals to permit charge transfer between them and in which switches from a second set of switches couple capacitor terminals of capacitors to either a high-voltage or a low-voltage terminal includes cycling the switches through a sequence of states, each state defining a corresponding configuration of the switches. At least three of the states define different configurations of the switches. During each of the configurations, charge transfer is permitted between a pair of elements, one of which is a first capacitor and another of which is either a second capacitor or the first terminal.

RELATED APPLICATIONS

Under 35 USC 120 this application is a continuation of U.S. applicationSer. No. 16/506,252, filed Jul. 9, 2019, which is a continuation of U.S.application Ser. No. 16/185,273, filed on Nov. 9, 2018, now U.S. Pat.No. 10,348,195, issued on Jul. 9, 2019, which is a continuation of U.S.application Ser. No. 15/126,050, filed on Sep. 14, 2016, now U.S. Pat.No. 10,128,745, issued on Nov. 13, 2018, which is the national phaseunder 35 USC 371 of International Application No. PCT/US2015/019579,filed on Mar. 10, 2015, which claims the benefit of the Mar. 14, 2014priority date of U.S. Provisional Application 61/953,270, the contentsof which are herein incorporated by reference.

FIELD OF INVENTION

This invention relates to control for charge pumps to balance charge.

BACKGROUND

Patent Publication WO 2012/151466, published on Nov. 8, 2012, andincorporated herein by reference, describes configurations of chargepumps, also known as switched capacitor converters, in which the sourceand/or load comprise regulating/regulator circuits. In some examples,the load can effectively comprise a current source and/or load ratherthan present a constant voltage in an example of what is referred to as“adiabatic” operation of a charge pump. Regulating/regulator circuits,such as switch-mode power converters, behave as current loads/sources.Therefore, current loads/sources and regulating/regulator circuits areinterchangeable for the purpose of this disclosure.

Although use of a current-based load (and/or source) may improveefficiency as compared to a purely or substantially voltage-based load(and/or source), internal energy losses may remain, for example, due toredistribution of charges within the charge pump.

SUMMARY

One effect of using a current-based load (and/or source) with a chargepump is that there may be situations in which a conventional switchtiming used with voltage-based loads and/or sources results in chargeimbalance across capacitors, which can result in loss of efficiency, forexample, due to charge redistribution immediately after switchingbetween configurations in the charge pump.

In one aspect, in general, an approach to improving efficiency of acharge pump using adiabatic charge transfer makes use of three or morestates, each corresponding to a configuration of switches couplingcapacitors to one another and/or the input and output terminals of thecharge pump. By introducing an appropriate sequence of more than twostates in which charge is transferred to or from capacitors, andselecting the duration those states are occupied in each operating cycleof the charge pump, charge transfer in and out of each capacitor isbalanced over the operating cycle, thereby avoiding or greatly reducingcharge redistribution at state transitions and its associated powerlosses that lead to inefficiency.

In one aspect, the invention features an apparatus for coupling tocapacitors to form a charge pump circuit. Such an apparatus includes afirst and second set of switch elements and a controller circuit. Thefirst set of switch elements comprises switch elements that areconfigured to couple terminals of capacitor elements to permit chargetransfer between the capacitors. The second set of switch elementscomprises switch elements that are configured to couple terminals of atleast some of the capacitor elements to a first terminal, which iseither a high voltage terminal or a low voltage terminal. The controllercircuit is coupled to the switch elements and configured to cycle theswitch elements through a sequence of states. Each state defines acorresponding configuration of the switch elements. At least three ofthe states define different configurations of the switch elementspermitting charge transfer between a pair of elements. The pair ofelements is either a pair of capacitors, or a capacitor and a terminal.The configured cycle of states provides a voltage conversion between thehigh voltage terminal and the low voltage terminal.

In some embodiments, there are terminals for coupling the switchelements to the capacitors.

Other embodiments include the capacitors themselves. In theseembodiments, the capacitors, when coupled to the switch elements, definea charge pump circuit.

Some embodiments comprise an integrated circuit. In these embodiments,at least part of the charge pump circuit and at least part of thecontroller circuit are formed in a single integrated circuit.

Also among the embodiments are those that include a regulator circuit.In these embodiments, the regulator circuit is coupled to at least oneof the high voltage terminal and the low voltage terminal of the chargepump circuit. In some of these embodiments, the regulator circuit isconfigured to provide a current load at the low voltage terminal of thecharge pump circuit. In others, the regulator circuit is configured tooperate as a current source at the low voltage terminal of the chargepump circuit. In yet others, the regulator circuit is configured toprovide a current load at the high voltage terminal of the charge pumpcircuit, or to operate as a current source at the high voltage terminalof the charge pump circuit, or to cause a pulsed current to pass betweenthe regulator circuit and the charge pump circuit. In the latter case,the charge pump operates in a pulse cycle having a first fraction,during which the pulsed current is a first constant current, and asecond fraction, during which the pulsed current is greater in magnitudethan the second constant current. In many cases, the second constantcurrent is substantially zero or even equal to zero. Typically, thefirst constant current is substantially larger than the second constantcurrent.

In some embodiments, a regulator circuit is configured to control anaverage current passing between the regulator circuit and the chargepump circuit.

In those embodiments that feature a regulator, a great many regulatortypes can be used. These include regulators that are switch-mode powerconverters, or buck converters, or even magnetic filters.

In some embodiments, the controller is configured to maintain each statefor a corresponding duration of a fraction of a charge pump cycle time.The durations of these states are selected to maintain a balancedcharging and discharging of each of the capacitors through the sequenceof states of each cycle.

In other embodiments, the controller is configured to select durationsof the states to reduce redistribution of charge among the capacitorsupon state transitions.

When coupled to the terminals of the capacitor elements, the switchelements define any of a variety of charge pump circuits. Examplesinclude a multi-phase charge pump, a single-phase charge pump, amulti-stage charge pump, and a cascade multiplier.

Also among the embodiments are those in which the controller isconfigured to receive sensor signals from at least one of the first andsecond sets of switch elements and to adaptively adjust cycling of theswitch elements through the sequence of states based at least in part onthe sensor signals.

In some embodiments, there are two regulator circuits. A regulatorcircuit is coupled to the high voltage terminal of the charge pumpcircuit. Meanwhile, a second regulator circuit is coupled to the lowvoltage terminal of the charge pump circuit. Either the first or secondregulator can be a magnetic filter. Among these embodiments are those inwhich the controller is configured to receive sensor signals from atleast one of the first and second sets of switch elements and toadaptively adjust cycling of the switch elements through the sequence ofstates based at least in part on the sensor signals.

In another aspect, the invention features a method for operating acharge pump in which switch elements from a first set of switch elementsare configured to couple terminals of capacitor elements to permitcharge transfer between the capacitors, and in which switch elementsfrom a second set of switch elements are configured to couple terminalsof capacitor elements to either a high voltage terminal or a low voltageterminal. Such a method includes causing a voltage conversion betweenthe high voltage terminal and the low voltage terminal. Causing thisvoltage conversion includes cycling the switch elements through asequence of states. Each state defines a corresponding configuration ofthe switch elements. At least three of the states define differentconfigurations of the switch elements permitting charge transfer betweena pair of elements. The pair of elements is either a pair of capacitorsor a capacitor and a one of the terminals.

Some practices of the invention include maintaining an average currentpassing between a regulator circuit and the charge pump circuit. Othersinclude regulating a current at the first terminal, thereby maintainingan average current passing between a regulator circuit and the chargepump circuit.

In other practices, cycling the switch elements through a sequence ofstates includes maintaining each state for a corresponding duration of afraction of a charge pump cycle time. This can also include selectingthe durations of the states are selected to maintain a balanced chargingand discharging of each of the capacitors through the sequence of statesof each cycle.

Some practices of the invention include controlling an average currentbetween a regulator circuit and the charge pump circuit.

Other practices include coupling a regulator circuit to the firstterminal. Among these are practices that include causing the regulatorcircuit to provide a current load at the low voltage terminal of thecharge pump circuit, causing the regulator circuit to provide a currentload at the high voltage terminal of the charge pump circuit, causingthe regulator circuit to operate as a current source at the low voltageterminal of the charge pump circuit, causing the regulator circuit tooperate as a current source at the high voltage terminal of the chargepump circuit, and causing a pulsed current to pass between a regulatorcircuit and the charge pump circuit.

Some practices include coupling the switch elements from the first andsecond sets of switch elements to the terminals of the capacitorelements. This can result in forming a multi-phase charge pump, asingle-phase charge pump, a multi-stage charge pump, or a cascademultiplier.

Those practices that involve a regulator include selecting the type ofregulator. This can include selecting the regulator to be a switch-modepower converter, selecting the regulator to be a buck converter, orselecting the regulator to be a magnetic filter.

Some practices also include receiving sensor signals from at least oneof the first and second sets of switch elements and adaptively adjustingthe cycling of the switch elements through the sequence of states basedat least in part on the sensor signals.

Some practices involve the use of two regulators. These practicesfurther include coupling a first regulator to the high voltage terminaland coupling a second regulator to the low voltage terminal. One of theregulators can be a magnetic filter while the other is a converter.Among these practices are those that also include controlling least oneof the first and second sets of switch elements and adaptively adjustingthe cycling of the switch elements through the sequence of states basedat least in part on sensor signals received from at least one of saidfirst and second sets of switch elements.

Other features and advantages of the invention are apparent from thefollowing description, and from the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a single-phase 5:1 charge pump with avoltage source and a current load.

FIGS. 2A and 2B are schematic diagrams of the circuit of FIG. 1 instates 1 and 2, respectively, of the switch configuration.

FIGS. 3A, 3B, and 3C are schematic diagrams of the circuit of FIG. 1 instates 1a, 1b, and 2, respectively.

FIG. 3D is a set of waveforms showing the voltage across each capacitorin FIGS. 3A-3C during the operation of the charge pump.

FIGS. 4A, 4B, and 4C are schematic diagrams of the circuit of FIG. 1 inalternative definitions of states 1a, 1b, and 2, respectively.

FIG. 4D is a set of waveforms showing the voltage across each capacitorin FIGS. 4A-4C during the operation of the charge pump.

FIG. 5 is a schematic diagram of a single-phase 6:1 charge pump with avoltage source and a current load.

FIGS. 6A, 6B, 6C, and 6D are schematic diagrams of the circuit of FIG. 5in states 1a, 1b, 2a, and 2b, respectively.

FIG. 7 is a schematic diagram of a two-phase 5:1 charge pump with avoltage source and a current load.

FIGS. 8A and 8B are schematic diagrams of the circuit of FIG. 7 instates 1a and 1b, respectively.

FIG. 9 is a schematic of a two-phase 3:1 series-parallel charge pumpwith a voltage source and a current load.

FIGS. 10A, 10B, 10C, and 10D are schematic diagrams of the circuit ofFIG. 9 in states 1a, 1b, 2a, and 2b, respectively.

FIGS. 11A and 11B are schematic diagrams of the circuit of FIG. 7 instates 1a and 1b, respectively with current skew.

FIGS. 12, 13, and 14 are block diagrams of power converters.

DETAILED DESCRIPTION

A first example charge pump 110 is shown in FIG. 1 to illustrate asource of charge imbalance in the operation of such a charge pump. Thecharge pump 110 is a cascade multiplier configured to nominally providea 5:1 (i.e., M=5) step-down in voltage such that an output voltageV_(OUT) (volts) is one-fifth of an input voltage V_(IN) (volts). Fourcapacitors (labeled C₁ to C₄) are used with switches (labeled S₁ to S₉)on both terminals of each capacitor to store a fraction of the inputvoltage V_(IN) and transfer charge from one capacitor to the next. Thecapacitors closest to the V_(IN) and V_(OUT) terminals are labeled C₁and C₄, respectively, and are referred to below as the “outer”capacitors, while the remaining capacitors labeled C₂ and C₃ arereferred to below as the “inner” capacitors. As further notation, thevoltage and charge on a capacitor C_(k) are denoted V_(k) and Q_(k),respectively. Unless otherwise indicated, the capacitors are treated asideally having identical capacitance C (Farads).

The charge pump 110 is operated by controlling a set of switches (S₁through S₉) that cause charge to pass between the capacitors and betweenthe terminals and the capacitors. The control of the switches of thecharge pump 110 can be represented as a cycle through a series ofstates, where each state is associated with a particular configurationof the set of switches (i.e., a particular setting of open-circuit(non-conducting) and closed-circuit (conducting) configuration of eachof the switches).

One mode of operation of the charge pump 110 shown in FIG. 1 uses acycle of two states. In a first state, namely state 1, the switcheslabeled “1” (i.e., S₁, S₃, S₅, S₇, S₈) are closed and the switcheslabeled “2” (i.e., S₂, S₄, S₆, S₉) are open. In a second state, namelystate 2, the switches labeled “1” are open and the switches labeled “2”are closed. These configurations of switches are shown in tabular form(“1” indicating the switch is closed and “0” indicating that the switchis open) as follows:

Switch State S₁ S₂ S₃ S₄ S₅ S₆ S₇ S₈ S₉ State 1 1 0 1 0 1 0 1 1 0 State2 0 1 0 1 0 1 0 0 1

Note that in practice, additional states may be needed in which all or asufficient set of switches are open such that charge is not passing toor from the capacitors without affecting the overall function of thecharge pump 110. This occurs, for example, in a “break before make”approach to avoid the necessity of truly instantaneous switching.However, for the analysis of the ideal behavior below, such additionalstates are not generally considered because these additional states donot involve a transfer of charge and will not affect the outcome of theanalysis.

A complete cycle of the charge pump 110 has a sequence of two states,state 1 followed by state 2. A first phase node P₁ couples with thenegative terminal of the capacitors C₁, C₃, and a second phase node P₂couples with the negative terminal of the capacitors C₂, C₄. The voltageat the first phase node P₁ alternates between ground and the outputvoltage V_(OUT), and the voltage at the second phase node P₂ is out ofphase with the first phase node P₁.

In steady-state operation, the capacitors C₁ to C₄ have nominal voltagesacross their terminals that are multiples of the nominal output voltage:V ₁ ^((nom))=4·V _(OUT) ^((nom))=(4/5)·V _(IN)V ₂ ^((nom))=3·V _(OUT) ^((nom))=(3/5)·V _(IN)V ₃ ^((nom))=2·V _(OUT) ^((nom))=(2/5)·V _(IN)V ₄ ^((nom))=1·V _(OUT) ^((nom))=(1/5)·V _(IN)

For example, when the input voltage V_(IN) equal to 25.0 (volts), thenominal voltages across the capacitors C₁-C₄ are 20.0, 15.0, 10.0, and5.0 (volts), respectively, and the nominal output voltage V_(OUT) is 5.0(volts). The actual voltages across the capacitors vary around thesenominal values (i.e., the voltage exhibits “ripple”) during a cycle ofthe successive states of operation of the charge pump 110, denoted asV _(k) =V _(k) ^((nom)+v) _(k).In this example, the output terminal of the charge pump 110 is treatedas being coupled to a current load, with current I_(OUT). In someexamples, this current is assumed constant. More generally, as discussedfurther below, the current may be pulsed with a constant averageĪ_(OUT)=D·I_(OUT) ^((peak)), where D is the duty cycle (a fractionbetween zero and one) of the pulsed current load. This is a goodrepresentation of the behavior of a buck converter. In general, thecurrent-load's switching frequency is an integer multiple of that chargepump's switching frequency. For example, it may be 2×, 3×, 10×, 100× thecharge pump's switching frequency. In some examples, the current may beconstant during a state, but have different values during each state.Furthermore, state transition instants are preferably chosen to occurduring the zero-current part of the output current duty cycle, therebyreducing switching losses with non-ideal (e.g., transistor) switches.But for the sake of discussion of this first example, only the constantcurrent case is considered.

FIGS. 2A-2B show the equivalent circuits of the charge pump 110 in FIG.1 for state 1 and state 2, respectively. In state 1, energy istransferred from the V_(IN) terminal to the outer capacitor C₁, betweenthe inner capacitors C₂, C₃, and from the outer capacitor C₄ to theV_(OUT) terminal. In state 2, energy is transferred between thecapacitors and to the load at the V_(OUT) terminal.

During state 1, the outer capacitors C₁, C₄ carry a current of0.4·I_(OUT) while the inner capacitors C₂, C₃ each carry a current of0.2·I_(OUT). This is half the current through the outer capacitors C₁,C₄. Therefore, if state 1 has a state-duration time t₁, then the changein charge on the outer capacitors C₁, C₄, denoted ΔQ_(k,j) as the changein charge on capacitor C_(k) during state j, satisfies+ΔQ _(1,1) =−ΔQ _(4,1) =t ₁·0.4·Ī _(OUT)while the change in charge on the inner capacitors C₂, C₃ during state 1satisfies−ΔQ _(2,1) =+ΔQ _(3,1) =t ₁·0.2·Ī _(OUT).Note that the inner capacitors C₂, C₃ are connected in series while theouter capacitors C₁, C₄ are the only elements in their respective paths,causing the current to divide accordingly by the number of seriescapacitors.

During state 2, every capacitor carries a current of 0.5·I_(OUT). Theinner capacitors C₂, C₃ are always in a series connection with anothercapacitor in either state while the outer capacitors C₁, C₄ have asimilar series connection only during state 2. The current flow polaritythrough each capacitor changes back and forth from one state to the nextstate as needed to charge and discharge the capacitor and maintain aconstant average voltage across the capacitor.

If the charge pump 110 were controlled at a 50% duty cycle witht₁=t₂=0.5·T_(SW), where T_(SW) is the total duration of the switchingcycle, the net charge across each cycle of two states on each capacitorC_(k), ΔQ_(k)=ΔQ_(k,1)+ΔQ_(k,2) would not be zero. A consequence of thiswould be that the net charge and average voltage on the capacitors maydrift over successive cycles and/or may cause a sizeable redistributionof charge at each state transition. Neither of these would be desirable.

An alternative three-state control of the charge pump 110 shown in FIG.1 uses first, second, and third states, which are labeled “1a”, “1b”,and “2”. The configuration of the switches in these states is shown intabular form as follows:

Switch State S₁ S₂ S₃ S₄ S₅ S₆ S₇ S₈ S₉ State 1a 1 0 0 0 1 0 1 1 0 State1b 0 0 1 0 0 0 1 1 0 State 2 0 1 0 1 0 1 0 0 1

The equivalent circuits in each of these states are shown in FIGS.3A-3C, respectively. Note that in state 1a, a current of 0.5·I_(OUT)passes through each of the capacitors C₁, C₄ (with opposite voltagepolarities), in state 1b, a current of 1.0·I_(OUT) passes through thecapacitors C₂, C₃, and in state 2, a current of 0.5·I_(OUT) passesthrough all four capacitors. A suitable selection of state-durationstimes t_(1a), t_(1b), t₂ to balance the total change in charge in eachcycle must satisfy the set of equations:ΔQ ₁=0=+0.5t _(1a)−0.5t ₂ΔQ ₂=0=−1.0t _(1b)+0.5t ₂ΔQ ₃=0=+1.0t _(1b)−0.5t ₂ΔQ ₄=0=−0.5t _(1a)+0.5t ₂T _(SW)=+1.0t _(1a)+1.0t _(1b)+1.0t ₂where the set of equations are satisfied witht _(1a)=0.4·T _(SW)t _(1b)=0.2·T _(SW)t ₂=0.4·T _(SW)

Assuming the state-duration times above, FIG. 3D illustrates thevoltages V₁-V₄ across the capacitors C₁-C₄ in FIGS. 3A-3C when thecharge pump 110 has an input voltage V_(IN) equal to 25.0 volts. Thisyields an output voltage V_(OUT) with average voltage of approximately5.0 volts as shown in the FIG. 3D.

Another three-state approach to controlling the charge pump 110 of FIG.1 uses a different sequence of states with switch configurations andcorresponding equivalent circuits shown in FIGS. 4A-4C, respectively.The configuration of switches in the three states is shown in tabularform as:

Switch State S₁ S₂ S₃ S₄ S₅ S₆ S₇ S₈ S₉ State 1a 1 0 1 0 1 0 1 1 0 State1b 0 0 1 0 0 0 1 1 0 State 2 0 1 0 1 0 1 0 0 1

An analysis as presented above applied to this definition of the statesyields state-duration times that satisfy the charge balance equations oft _(1a)=0.5·T _(SW)t _(1b)=0.1·T _(SW)t ₂=0.4·T _(SW)

Assuming the state-duration times above, FIG. 4D illustrates thevoltages V₁-V₄ across the capacitors C₁-C₄ in FIGS. 4A-4C when thecharge pump 110 has an input voltage V_(IN) equal to 25.0 volts. Thisyields an output voltage V_(OUT) with average voltage of approximately5.0 volts as shown in FIG. 4D. Notice how the shape of the waveforms inFIG. 4D differ from those in FIG. 3D.

A consideration of the sum of the RMS (root mean squared) currentsthrough the capacitors shows that these state definitions yield a lowervalue than that of the previously described three-state configuration(FIGS. 3A-3C). In a non-ideal implementation of the charge pump 110, inwhich resistances including resistances in series with the capacitorscause power loss, a lower RMS current is associated with smaller powerloss. Therefore, these state configurations may be preferable.

Note that different sequences of states can still result in chargebalance over the repeating cycle. For example, the state sequence1a-1b-2-1a-1b-2 . . . can be replaced with the sequence 1b-1a-2-1b-1a-2. . . using the same state-duration times as determined above.

Other state definitions and timing also follow the approach outlinedabove. For instance, two additional approaches for the M=5 case areshown below in tabular form:

Switch State S₁ S₂ S₃ S₄ S₅ S₆ S₇ S₈ S₉ Duration State 1a 0 0 1 0 1 0 11 0 0.3 · T_(SW) State 1b 1 0 1 0 0 0 1 1 0 0.3 · T_(SW) State 2 0 1 0 10 1 0 0 1 0.4 · T_(SW)and

Switch State S₁ S₂ S₃ S₄ S₅ S₆ S₇ S₈ S₉ Duration State 1a 1 0 0 0 0 0 1X 0 0.2 · T_(SW) State 1b 0 0 0 0 1 0 X 1 0 0.2 · T_(SW) State 1c 0 0 10 0 0 1 1 0 0.2 · T_(SW) State 2 0 1 0 1 0 1 0 0 1 0.4 · T_(SW)where X indicates that the switch can either be open or closed.

The multi-state approach presented above for the M=5 circuit of FIG. 1may be extended directly to other odd values of M. Generally, in state1a, capacitor C₁ is in parallel with capacitor C_(M-1), and when M≥5 inparallel with series connections of C₂ and C₃, through C_(M-3) andC_(M-2). State 1b has the parallel connection of the series of C₂ andC₃, through C_(M-3) and C_(M-2), and state 2 has the parallel connectionof the series C₁ and C₂ through C_(M-2) and C_(M-1). A closed form ofthe state-duration times for general odd M can then be expressed ast _(1a)=(M+5)/(4M)·T _(SW)t _(1b)=(M−3)/(4M)·T _(SW)t ₂=(M−1)/(2M)·T _(SW)

A similar approach can be applied to situations where M is even.Referring to FIG. 5, a 6:1 (M=6) cascade multiplier type charge pump 110is shown that includes ten switches labeled S₁ to S₁₀ and fivecapacitors labeled C₁ to C₅. The configurations for the switches in eachof four states: 1a, 1b, 2a, and 2b, are shown in the table below. Theequivalent circuits in each of these states are shown in FIGS. 6A-6D,respectively.

Switch State S₁ S₂ S₃ S₄ S₅ S₆ S₇ S₈ S₉ S₁₀ State 1a 1 0 1 0 1 0 0 1 1 0State 1b 0 0 1 0 1 0 0 1 1 0 State 2a 0 1 0 1 0 1 1 0 0 1 State 2b 0 1 01 0 0 1 0 0 1

Applying the type of analysis described above, the state-duration timesto achieve a balancing of charge transfer through the cycle of statesyields:t _(1a)=1/3·T _(SW)t _(1b)=1/6·T _(SW)t _(2a)=1/3·T _(SW)t _(2b)=1/6·T _(SW)

As with M being an odd case, a general solution for arbitrary M beingeven yields the solution:t _(1a)=(M−2)/(2M)·T _(SW)t _(1b)=1/M·T _(SW)t _(2a)=(M−2)/(2M)·T _(SW)t _(2b)=1/M·T _(SW)

The approach described above is applicable to multi-phase charge pumpsas well. For example, FIG. 7 shows a two-phase M=5 cascade multipliertype charge pump 110 that includes fourteen switches labeled S_(1a) toS_(7b) and eight capacitors labeled C_(1a) to C_(4b).

The configurations for the switches in one possible four-state approach(with states labeled 1a, 1b, 2a, 2b) are shown in the table below:

Switch State S_(1a) S_(1b) S_(2a) S_(2b) S_(3a) S_(3b) S_(4a) S_(4b)S_(5a) S_(5b) S_(6a) S_(6b) S_(7a) S_(7b) State 1 0 0 1 0 1 0 1 0 0 0 11 0 1a State 0 0 0 1 0 1 0 1 0 1 0 1 1 0 1b State 0 1 1 0 1 0 1 0 0 0 10 0 1 2a State 0 0 1 0 1 0 1 0 1 0 1 0 0 1 2b

FIGS. 8A-8B show the equivalent circuits for states 1a and 1b,respectively. The circuits for states 2a and 2b are equivalent (i.e.,interchanging the “a” and “b” elements of the circuit). Applying thecharge balance constraints for this circuit yields the state-durationtimes of 0.25·T_(SW) for each of the four states as shown below:t _(1a)=1_(2a)=0.25·T _(SW)t _(1b) =t _(2b)=0.25·T _(SW)Note that in this example, the input current from the V_(IN) terminal iszero during states 1b and 2b while non-zero during states 1a and 2a at acurrent of 0.4·I_(OUT), yielding an average input current of0.2·Ī_(OUT)=Ī_(OUT)/M as expected.

Referring to FIG. 7, a parallel arrangement of two sections as shown inFIG. 1; the timing of each section is 90° out of phase, such that onesection has the switch configuration of state 1a while the other sectionhas the switch configuration of state 1b, and so forth. Note that inthis parallel arrangement, the average input current is0.2·Ī_(OUT)=Ī_(OUT)/M in each cycle of operation.

The approaches described above are applicable to a wide range of chargepump topologies. As a further example, an FIG. 9 shows a M=3 two-phaseseries-parallel charge pump 110 that includes fourteen switches labeledS_(1a) to S_(7b) and four capacitors labeled C_(1a) to C_(2b). Theconfiguration of switches in the four states is shown in tabular formas:

Switch State S_(1a) S_(1b) S_(2a) S_(2b) S_(3a) S_(3b) S_(4a) S_(4b)S_(5a) S_(5b) S_(6a) S_(6b) S_(7a) S_(7b) State 1 0 1 0 1 0 0 1 0 1 0 00 0 1a State 1 0 1 0 1 0 0 0 0 0 0 1 0 1 1b State 0 1 0 1 0 1 1 0 1 0 00 0 0 2a State 0 1 0 1 0 1 0 0 0 0 1 0 1 0 2b

Equivalent circuits for the four states are shown in FIGS. 10A-10D.Charge balance is achieved with a state-duration time of 0.25·T_(SW) foreach state, yielding an average input current from V_(IN) in each stateand cycle of (1/3)·Ī_(OUT).

In the analysis above, the average current Ī_(OUT) is assumed to be thesame during all state-duration times, therefore, the charge transfersare proportional to t_(j)·Ī_(OUT). In an alternative approach, theaverage output current may be controlled to be different for differentstates so that the charge transfers in state j are proportional tot_(j)·Ī_(OUT,j) where both the state-duration time t_(j) and the averagecurrent Ī_(OUT,j) are determined according to the constraint equations.In some examples, the state-duration times may be further (fully orpartially) constrained for other considerations, for example, to avoidshort state-duration times which might cause EMI (electromagneticinterference). An example, where such variable and periodic control ofoutput current may be effective is when driving one or more LEDs (lightemitting diode) in series or in parallel, where the variation in currentdoes not appreciably cause perceptible variation in light output.

The approach described above can be applied to the two-phase M=5 cascademultiplier type charge pump 110 of FIG. 7. One possible four-stateapproach (with states labeled 1a, 1b, 2a, 2b) has equivalent circuits asshown in FIGS. 11A-11B for states 1a and 1b, respectively. The circuitsfor states 2a and 2b are equivalent (i.e. interchanging the “a” and “b”elements of the circuit). The configuration of switches in the fourstates is shown in tabular form as:

Switch State S_(1a) S_(1b) S_(2a) S_(2b) S_(3a) S_(3b) S_(4a) S_(4b)S_(5a) S_(5b) S_(6a) S_(6b) S_(7a) S_(7b) State 1 0 0 0 0 0 0 0 0 1 0 11 0 1a State 0 0 0 1 0 1 0 1 0 0 0 1 1 0 1b State 0 1 0 0 0 0 0 0 1 0 10 0 1 2a State 0 0 1 0 1 0 1 0 0 0 1 0 0 1 2b

With state-duration times of 0.25·T_(SW) for each of the four states, itbecomes necessary to apply a current skew, I_(SKEW), to the output loadin each state to achieve charge balance over a cycle of the four states.In this example, a negative current skew of 0.2·I_(OUT) during states 1aand 2a, and a positive current skew of 0.2·I_(OUT) during states 1b and2b will achieve charge balance in all capacitors over a cycle, where theaverage output current across each cycle of four states is I_(OUT). Inother words, the output load current during states 1a and 2a is0.8·I_(OUT) and the output load current during states 1b and 2b is1.2·I_(OUT). The magnitude of the applied current skew is the same inall four states, but the polarity of the current skew changes back andforth between positive and negative from one state to the next. For atwo-phase charge pump with this four-state approach and 0.25·T_(SW)state-duration times, a general solution for arbitrary M yields thefollowing solution for the magnitude of the applied current skew,I_(SKEW):

$I_{SKEW} = {{\frac{4 - M}{M}}I_{OUT}}$

It should be understood that the description above focuses on analysisof idealized circuits with ideal switches, ideal current, voltagesources, and resistance-free circuit paths. In practice, switches areimplemented, for instance, with transistors, which generally exhibitinternal resistance and capacitive characteristics. The output currentload may be implemented using an inductor such that during the part ofthe duty cycle modeled as a constant current, the current in factfluctuates as energy is transferred from the charge pump to theinductor. Physical capacitors may have slightly different capacitances,and therefore the ideal analysis for charge balancing may not be exactlycorrect. Nevertheless, the approach presented above is applicable tonon-ideal implementations of the approach, either exactly, or accountingfor the non-ideal nature of the circuit for example, determining thestate durations to achieve charge balance in a real rather than an idealcircuit, for example, using numerical circuit simulation techniques.

Implementations of a charge pump controlled according to one or more ofthe approaches described above may use a controller that is configuredto follow a state sequence as described and to set the switchesaccordingly. Referring to FIG. 12, an example of a power converter 100includes a charge pump 110 coupled to a controller 120 providing controlsignals on path 132 and receiving sensor signals on path 134. The chargepump 110 includes capacitors 112 and switches 114. A terminal 116 (e.g.,a high voltage terminal) couples the charge pump 110 to a power source150, for example, to a voltage source (e.g., at twenty-five volts).Another terminal 118 couples the charge pump 110 to a first regulatorcircuit 130, which is coupled to a load 140. A controller 120 includes aprogrammable processor 122 configured with configuration data 124(and/or processor instructions), which impart functionality on thecontroller 120.

In some examples, the controller 120 also controls the first regulatorcircuit 130, for example, to maintain a common underlying clocking ratefor both the charge pump 110 and the first regulator circuit 130 (e.g.,switching the first regulator circuit 130 at a multiple 2×, 4×, 10×,100×, etc. of the cycle frequency of the charge pump 110). In someimplementations, the controller 120 is integrated in whole or in part inan integrated device that includes at least some of the switches 114(e.g., transistors).

An alternative power converter 101 is illustrated in FIG. 13, where asecond regulator circuit 160 is coupled between the power source 150 andthe charge pump 110 instead of between the load 140 and the charge pump110 as in FIG. 12. In some examples, the controller 120 controls theload 140 to facilitate charge balancing of the capacitors 112 within thecharge pump 110. In other examples, the controller 120 controls thesecond regulator circuit 160 and in even other examples, the controller120 controls both the load 140 and the second regulator circuit 160.

One more alternative power converter 102 is illustrated in FIG. 14. Thisexample is a combination of the power converters 100, 101. In thisimplementation, there is a first regulator circuit 130 coupled betweenthe load 140 and the charge pump 110; and a second regulator circuit 160coupled between the power source 150 and the charge pump 110. In someexamples the controller 120 controls at least the first regulatorcircuit 130 or the second regulator circuit 160, to maintain a commonunderlying clocking.

In other examples, either the first regulator circuit 130 or the secondregulator circuit 160 is a magnetic filter, such as an LC filter,instead of a converter. If the first regulator circuit 130 is a magneticfilter, then the regulation capability of the power converter 102 isonly accomplished by the second regulator circuit 160 and adiabaticoperation is in part possible due to the first regulator circuit 130acting as a current load. Similarly, if the second regulator circuit 160is a magnetic filter, then the regulation capability of the powerconverter 102 is only accomplished by the first regulator circuit 130and adiabatic operation is in part possible due to the second regulatorcircuit 160 acting as a current source.

It should be understood that in practice, the devices are not ideal, forexample, with the capacitors 112 not necessarily having identicalcapacitances, and with non-zero resistances in circuit paths and throughthe switches 114 in the charge pump 110. In some examples, thecontroller 120 controls the switches 114 according to the idealizedanalysis. In other examples, the effect of non-idealized characteristicsare taken into account in determining the state durations, for example,by explicit circuit analysis (e.g., simulation) or adaptively byadjusting the relative state durations to achieve charge balance duringstate cycles based upon sensor signals on path 134. In some examples,the controller 120 is software configurable, for example, allowingspecific state timing to be configured after the device is fabricated.In some examples, the controller 120 is fully or at least partiallyimplemented in application-specific logic that is specified with theother circuit components of the device.

The charge pump 110 can be implemented using many different charge pumptopologies such as Ladder, Dickson, Series-Parallel, Fibonacci, andDoubler. Similarly, suitable converters for the regulator circuits 130,160 include Buck converters, Boost converters, Buck-Boost converters,non-inverting Buck-Boost converters, Cuk converters, SEPIC converters,resonant converters, multi-level converters, Flyback converters, Forwardconverters, and Full Bridge converters.

It is to be understood that the foregoing description is intended toillustrate and not to limit the scope of the invention, which is definedby the scope of the appended claims. Other embodiments are within thescope of the following claims.

The invention claimed is:
 1. An apparatus comprising: a clock togenerate one or more timing signals; a charge pump coupled to at leastone inductor, the charge pump having an input port and an output portand comprising a plurality of capacitors interconnected via one or moresets of switches controllable to switch between a plurality of switchconfigurations, a particular switch configuration of the plurality ofswitch configurations to correspond to a particular state of a pluralityof states of the charge pump; and a controller to generate one or morecontrol signals based, at least in part, on the one or more timingsignals, the one or more control signals to control at least a dutycycle of the particular switch configuration of the plurality of switchconfigurations to reduce redistribution of charge between two or morecapacitors of the plurality of capacitors such that there issubstantially no total change in charge on at least one of the two ormore capacitors.
 2. The apparatus of claim 1, wherein the redistributionof charge to at least partially result from a charge imbalance withinthe charge pump to occur due, at least in part, to the at least oneinductor being coupled to the charge pump.
 3. The apparatus of claim 2,wherein the charge imbalance within the charge pump to comprise animbalance with respect to a total change in charge on the plurality ofcapacitors over a full operating cycle of the charge pump.
 4. Theapparatus of claim 3, wherein the plurality of states to comprise thefull operating cycle of the charge pump.
 5. The apparatus of claim 1,wherein the plurality of states to include at least a first, a second,and a third state having corresponding state duration times.
 6. Theapparatus of claim 5, wherein the corresponding state duration times tobe controlled by the controller to reduce the redistribution of chargebetween the two or more capacitors of the plurality of capacitors at theparticular state of the charge pump.
 7. The apparatus of claim 1,wherein the at least one inductor to be coupled to at least one of thefollowing ports of the charge pump: the input port; the output port; orany combination thereof.
 8. The apparatus of claim 1, wherein the atleast one inductor comprises at least one of the following: a regulator;a load; or any combination thereof.
 9. The apparatus of claim 8, whereinthe regulator comprises at least one of the following: a converter; amagnetic filter; or any combination thereof.
 10. The apparatus of claim9, wherein the converter comprises a buck converter; a boost converter;a buck-boost converter; a non-inverting buck-boost converter; a Cukconverter; a SEPIC converter; a resonant converter; a multi-levelconverter; a flyback converter; a forward converter; or a full bridgeconverter.
 11. The apparatus of claim 8, wherein the regulator tocontrol an average current between the regulator and the charge pump.12. The apparatus of claim 1, wherein the charge pump comprises amulti-phase charge pump; a single-phase charge pump; a multi-stagecharge pump; or a cascade multiplier.
 13. The apparatus of claim 1,wherein the one or more control signals to adaptively adjust the dutycycle of the particular switch configuration of the plurality of switchconfigurations based, at least in part, on one or more sensor signals tobe received from the one or more sets of switches.
 14. An apparatuscomprising: an integrated circuit (IC); the IC comprising a controllerto implement at least a three-state control of a charge pump includingtwo or more capacitors coupled to a plurality of switches along a chargetransfer path between an input port and an output port of the chargepump, the controller, during a plurality of successive operating cyclesof the charge pump, to control operation of the plurality of switches sothat the charge pump is able to transition from a first state to asecond state and to at least a third state, the first, the second, orthe third states to have corresponding duty cycles, wherein thecontroller, during at least one operating cycle of the plurality ofsuccessive operating cycles of the charge pump, to facilitate a totalchange in charge on the two or more capacitors based, at least in part,on the corresponding duty cycles of the first, the second, or the thirdstates such that the total change in charge on at least one of the twoor more capacitors is balanced, and wherein a net charge on the at leastone of the two or more capacitors does not substantially change.
 15. Theapparatus of claim 14, wherein the charge pump circuit comprises amulti-phase charge pump.
 16. The apparatus of claim 15, wherein themulti-phase charge pump to transition from a first phase to a secondphase and to subsequently transition from the second phase to the firstphase.
 17. The apparatus of claim 16, wherein the first, the second, andthe third states to be implemented for the first phase and/or for thesecond phase of the multi-phase charge pump.
 18. The apparatus of claim14, wherein the at least one of the two or more capacitors to hold aconstant amount of charge during at least one of the first, the second,and the third states.
 19. The apparatus of claim 14, wherein thecontroller to adaptively adjust the corresponding duty cycles of thefirst, the second, and the third states based, at least in part, on oneor more sensor signals to be received from one or more switches of theplurality of switches.
 20. The apparatus of claim 14, wherein thecontroller, during the at least one operating cycle of the plurality ofsuccessive operating cycles of the charge pump, to facilitate a voltageconversion between the input port and the output port of the chargepump.
 21. The apparatus of claim 14, wherein the charge pump to outputan average output current, the average output current to be maintained,at least in part, by the controller, at a substantially constant levelduring at least one of the following: the first state; the second state;the third state; or any combination thereof.